At a cost of more than $250 million, the Lower Olentangy Tunnel is nearing completion. The 3.5 mile long tunnel stretches from Olentangy River Road near the Spectrum Building and ends at Tuttle Park. The drill busted through the concrete wall of the tunnel Wednesday afternoon. It started its journey in February of last year. The City of Columbus is under two Ohio Environmental Protection Agency (OEPA) consent orders to improve water quality and reduce the potential for human contact with waterborne pollutants by reducing overflows from the sewer system into creeks and rivers during wet weather events. Columbus, like many cities across the country, had difficulty containing sewage overflows during heavy rains as its older pipes leaked into the sewer system. The city has pipes that date back to the 1800s. The city says the LOT will not only prevent sewage overflows from happening in the future, but will also add more water capacity —approximately 16 million more gallons of water — to handle future growth like the addition of Intel. Project developers say the tunnel is designed to handle a once in every 10-year heavy rain fall. When that happens, the massive concrete shaft can hold the water giving the water treatment plant time to handle the excess water. When the water is sent to the water treatment plant it will be pumped back into the Olentangy River. When asked how clean the water is that is being sent back into the river, Project Director for Columbus Water and Power Jeremy Cawley said it's potable. "It’s the same as what would come out of any other waste water treatment plant, it meets EPA standards,” Cawley said. The city says the tunnel should start accepting water around September of 2026. You can read more about the project here.